This invention relates to a method and apparatus for determining the efficacy of the lock-up mechanism of a torque converter.
Various machines are utilized to test transmissions used in automotive vehicles. These machines enable rebuilt transmissions to be tested apart from the vehicle and under simulated conditions of operation. Basically, the test machine comprises a test stand having thereon a prime mover/engine which powers the transmission under test. The transmission under test drives a simulated load connected to the output shaft of the transmission. Accordingly, the rebuilt transmission is mounted on the test stand, powered by the prime mover and operated as if installed on a vehicle.
Various performance parameters of the tested transmission may then be measured. It is desirable to test whether the power, generated by the prime mover, is being efficiently transmitted to the drive wheel(s)/load of the vehicle. Thus, I have found that the efficacy of the torque converter and the lock-up mechanism therein must be considered.
In normal operation, the torque converter uses oil as the fluid coupling medium to transfer the power of the rotating drive shaft to the input shaft of the transmission. Generally, the converter includes a housing having a first and second series of opposed windmill-like plates or vanes therein. The housing and "pump/driver" vanes are attached to the drive shaft of the engine. The opposed set of "turbine/driven" vanes is attached to the input transmission shaft. As the pump vanes are rotated by the rotating drive shaft there must be a medium to transfer the rotation of the pump vanes to the turbine vanes so as to drive the input shaft.
As there is no direct mechanical connection between the pump and the turbine, the converter housing is filled with oil. As the pump rotates it "flings" oil onto the turbine vanes. The oil being flung onto the turbine causes the turbine to rotate as well as the transmission shaft connected thereto.
A stator member system directs the oil being flung from the rotating turbine back against the turbine. As the redirected oil repeatedly contacts the turbine vanes, the forces on the turbine vanes increase resulting in torque multiplication. Torque multiplication occurs only when the pump is turning considerably faster than the turbine, such as during acceleration of the vehicle.
As the vehicle speed increases, the rotation of the turbine begins to "catch up" with the pump. The force of the oil being flung from the turbine is reduced as the turbine is taking up most of the energy. As there is no need to redirect the oil back onto the turbine, the stator is removed from its "normal" operation.
However, even at high speeds there is still an inherent inefficiency in directing the transfer of the rotation of the pump to the turbine via a fluid coupling medium. Thus, it is advantageous to mechanically couple or "lock-up" the rotation of the turbine to that of the pump side to reduce any "fluid-coupling" slippages and inefficiencies therebetween. A lock-up assembly has been provided to provide this connection. Generally, the lock-up assembly comprises a clutch plate connected to the input shaft of the transmission, a valve-controlled, fluid flow system and lock up solenoid. (It is understood that some lock-up assemblies are activated by non-electrical signals). When computer-like sensors detect a high r.p.m., designating that the car is in a high gear, an electric signal is delivered to the lock up solenoid. The energized solenoid closes a valve in the fluid flow system which allows oil to flow to the apply side of the clutch plate. The fluid pressure moves the plate into a position linking it with the converter housing. As the plate is now linked to the drive shaft, there is a direct drive between rotation of the engine drive shaft and the input shaft of the transmission. This direct connection eliminates any inherent slippage that may occur due to the normal fluid coupling.
Accordingly, my invention presents a method and performing apparatus of measuring the efficacy of the lockup mechanism of a torque converter. More particularly, I provide a method and performing apparatus to determine the time it takes the lock-up assembly to provide the direct-drive connection as measured from the time the assembly receives it lock-up command. This time parameter is then compared with a preestablished time parameter indicative of normal function of the lock-up mechanism.